All-fiber periodically Q-switched laser

Abstract

Q-switched fiber lasers provide a cheap and relatively simple means of generating nanosecond-scale high-energy optical pulses with high peak power. The pulse energy and peak power achievable in actively Q-switched fiber lasers is often limited by the Q-switching device. For example, coupling to any active modulator device (e.g. electrooptic modulator, Pockels cell) increases both the cavity length and intracavity loss, and often introduces low levels of reflection from interfaces of fiber-coupled elements. The latter imperfections can significantly limit the laser performance, e.g. limiting the maximum inversion before the onset of CW lasing, reducing the laser efficiency, and increasing the Q-switched pulse duration, resulting in reduced peak power and reduced pulse energy. Additionally, the large powers achieved in fiber lasers in recent years make damage an increasing concern, even at fiber ends and interfaces. Consequently all-fiber Q-switched lasers are receiving attention, e.g. using a modulated Bragg grating to modulate the cavity loss (Delgado-Pinar et al., 2006). Here we present a simple loss modulation technique using a vibrating fiber and mirror. The method combines the advantages of high dynamic range and high damage threshold. We demonstrate its application in a short all-fiber Q-switched laser.